Installed a W/H this morning. I could write a humorous short story, but instead I'll put out an inquiry regarding the vent piping, a type I hadn't seen before.
It was a double wall pipe, three-inch size, that didn't have any way to break into to accommodate a slightly taller water heater. I ended up with an ugly Mad Max patch job that probably destroyed my self-esteem for the next decade or so.
From the ceiling of the water heater alcove in the garage end wall, a nub came down a couple of inches and connected with a band to the first section of double-wall pipe, @16in long. Further down, another 16in section was crimped onto the first section. At the bottom was a four-inch nub, crimped onto the second section and attached to the old water heater.
I'm familiar with the double-wall pipe that has the push and turn connection system. No problem there. But I've never had to deal with this particular pipe before. I don't see any way to break into it to connect to the new w/h. It is crimped all the way around, plus being dinged together with a couple of dimples on either side below the connection.
I want my connections to look nice, and more often than not I get there. However, this is something new to me and I'd appreciate some output from anyone who has experience in dealing with this system. Thanks.

No picture?
I do recall I ran into something similar perhaps recently. I was expecting the twist pipe, but no.
I do carry a crimper with my tools, and pipe snips. Pretty handy at times.
I'm dreading the new rules for water heaters coming down the pike. There will be all kinds of changes, and some will need new venting. I will need to be a marraige counseler with some of the new stuff we will be installing.